The present invention relates in general to automotive air bag systems, and, more specifically, to a hidden air bag deployment door formed by an instrument panel substrate and a molded air bag chute.
Air bag deployment chute assemblies have been put into commercial use for the passenger side of an instrument panel of automotive vehicles. The chute assembly couples an air bag module (typically containing a folded canvas bag and chemical propellants for inflating the bag on command) to a door support panel or substrate of the instrument panel. A typical structure for a chute assembly includes a tubular outer chute wall, one or more door flaps, a flange surrounding the door area, and one or more hinge members or areas connecting the door flap(s) to the outer wall and flange.
For styling purposes, it is desirable for the air bag deployment door in the instrument panel to be invisible when viewed from the passenger compartment. In other words, the visible or “Class A” surface of the instrument panel is preferably seamless. Therefore, a pre-weakened seam is required in the substrate (on the “Class B” side) to facilitate tearing open of the door during air bag deployment. In order to prevent torn or severed pieces of the substrate from being expelled into the passenger cabin, the door flap(s) of the chute attach to the substrate door area so that the door flap and hinge act as a tether. A common method to attach the chute door flap and flange to the substrate has been by plastic welding, such as vibration welding, hot-plate welding, and the like.
For optimum protection of a passenger, the passenger-side air bag door is placed in or near the top surface of the instrument panel which results in the door being close to the front windshield of the vehicle. Consequently, impingement of the door against the windshield as it swings open during deployment of the air bag becomes a potential pitfall in the event the windshield could be damaged. Vehicle styling trends and a desire for improved aerodynamics often result in the slant (i.e., layback angle) of the windshield being increased and the front-to-back depth of the instrument panel being shortened. In addition, passenger air bags are becoming increasingly large and powerful, which raises the minimum required door size for accommodating deployment of the air bag. Consequently, the potential swing area of the air bag door becomes more likely to intersect with the windshield.
Due to its momentum from being forced open by the inflating air bag, the air bag door tends to swing beyond the opening size needed to expel the bag. To prevent this, it is known to attach an outer end of the door to the instrument panel via a tether. One or more tethers can be embedded in a chute assembly by overmolding or can be attached as a secondary operation. It would be desirable to avoid the added costs of components and/or assembly associated with tethers while both preventing door contact with the windshield and obtaining a sufficiently large door opening to accommodate a full capacity air bag.